base: add 'trace' function to base/log.h

The 'Genode::trace' convenience function prints messages to Genode's
trace buffer (if tracing is enabled).

issue #3294

repos/base/include/base/log.h

@@ -16,11 +16,13 @@
 
 #include <base/output.h>
 #include <base/lock.h>
+#include <trace/timestamp.h>
 
 namespace Genode {
 
 	class Log;
 	class Raw;
+	class Trace_output;
 }
 
 
@@ -101,6 +103,36 @@ class Genode::Raw
 };
 
 
+class Genode::Trace_output
+{
+	private:
+
+		Lock _lock { };
+
+		Output &_output;
+
+		void _acquire();
+		void _release();
+
+	public:
+
+		Trace_output(Output &output) : _output(output) { }
+
+		template <typename... ARGS>
+		void output(ARGS &&... args)
+		{
+			_acquire();
+			Output::out_args(_output, args...);
+			_release();
+		}
+
+		/**
+		 * Return component-global singleton instance of the 'Trace_output'
+		 */
+		static Trace_output &trace_output();
+};
+
+
 namespace Genode {
 
 	/**
@@ -140,6 +172,16 @@ namespace Genode {
 	 */
 	template <typename... ARGS>
 	void raw(ARGS &&... args) { Raw::output(args...); }
+
+
+  /**
+   * Write 'args' to the trace buffer if tracing is enabled
+   *
+   * The message is prefixed with a timestamp value
+   */
+	template <typename... ARGS>
+	void trace(ARGS && ... args) {
+		Trace_output::trace_output().output(Trace::timestamp(), ": ", args...); }
 }
 
 #endif /* _INCLUDE__BASE__LOG_H_ */

repos/base/lib/symbols/ld

@@ -80,6 +80,9 @@ _ZN6Genode11Sliced_heapD1Ev T
 _ZN6Genode11Sliced_heapD2Ev T
 _ZN6Genode12Address_infoC1Em T
 _ZN6Genode12Address_infoC2Em T
+_ZN6Genode12Trace_output12trace_outputEv T
+_ZN6Genode12Trace_output8_acquireEv T
+_ZN6Genode12Trace_output8_releaseEv T
 _ZN6Genode13Avl_node_base15_rotate_subtreeEPS0_bRNS0_6PolicyE T
 _ZN6Genode13Avl_node_base18_rebalance_subtreeEPS0_RNS0_6PolicyE T
 _ZN6Genode13Avl_node_base6_adoptEPS0_bRNS0_6PolicyE T
@@ -587,11 +590,11 @@ _ZThn8_N6Genode23Alarm_timeout_scheduler14handle_timeoutENS_8DurationE T
 _ZThn8_N6Genode23Alarm_timeout_schedulerD0Ev T
 _ZThn8_N6Genode23Alarm_timeout_schedulerD1Ev T
 _ZdlPv W
-_ZdlPvm W
 _ZdlPvPN6Genode11DeallocatorE T
 _ZdlPvPN6Genode9AllocatorE W
 _ZdlPvRN6Genode11DeallocatorE T
 _ZdlPvRN6Genode9AllocatorE W
+_ZdlPvm W
 _ZnajPN6Genode9AllocatorE T
 _ZnajRN6Genode9AllocatorE T
 _ZnamPN6Genode9AllocatorE T

repos/base/src/lib/base/default_log.cc

@@ -62,6 +62,18 @@ Log &Log::log()
 }
 
 
+static Trace_output *trace_ptr;
+
+Trace_output &Trace_output::trace_output()
+{
+	if (trace_ptr)
+		return *trace_ptr;
+
+	raw("Error: Missing call of init_log");
+	sleep_forever();
+}
+
+
 /**
  * Hook for support the 'fork' implementation of the noux libc backend
  */
@@ -95,5 +107,16 @@ void Genode::init_log(Parent &parent)
 		unmanaged_singleton<Buffered_log_output>(Write_fn());
 
 	log_ptr = unmanaged_singleton<Log>(*buffered_log_output);
+
+	/* enable trace back end */
+	struct Write_trace_fn { void operator () (char const *s) { Thread::trace(s); } };
+
+	typedef Buffered_output<Log_session::MAX_STRING_LEN, Write_trace_fn>
+	        Buffered_trace_output;
+
+	static Buffered_trace_output *buffered_trace_output =
+		unmanaged_singleton<Buffered_trace_output>(Write_trace_fn());
+
+	trace_ptr = unmanaged_singleton<Trace_output>(*buffered_trace_output);
 }
 

repos/base/src/lib/base/log.cc

@@ -59,3 +59,20 @@ void Raw::_release()
 	 */
 	_output().out_string("\033[0m\n");
 }
+
+
+void Trace_output::_acquire()
+{
+	_lock.lock();
+}
+
+
+void Trace_output::_release()
+{
+	/*
+	 * Add newline
+	 */
+	_output.out_string("\n");
+
+	_lock.unlock();
+}